CmdPal: Transparent window (#45159)

## Summary

This PR adds:
- Backdrop material customization
  - Alongside acrylic, the following options are now available:
  - Transparent background
  - Mica background
- Background material opacity
  - Lets you control how transparent the background is

## Pictures? Pictures!

<img width="1491" height="928" alt="image"
src="https://github.com/user-attachments/assets/ff4e9e06-fcf1-4f05-bc0a-fb70dc4f39be"
/>



https://github.com/user-attachments/assets/84e83279-afab-481e-b904-f054318c5d2f

<img width="977" height="628" alt="image"
src="https://github.com/user-attachments/assets/241a228d-af3f-448a-94a6-0a282218bd8c"
/>


## PR Checklist

- [x] Closes: #44197
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issues) -->
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
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- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
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for new binaries
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pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
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- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/AppearanceSettingsViewModel.cs

@@ -18,6 +18,8 @@ namespace Microsoft.CmdPal.UI.ViewModels;
 
 public sealed partial class AppearanceSettingsViewModel : ObservableObject, IDisposable
 {
+    private static readonly Color DefaultTintColor = Color.FromArgb(255, 0, 120, 212);
+
     private static readonly ObservableCollection<Color> WindowsColorSwatches = [
 
         // row 0
@@ -128,10 +130,13 @@ public sealed partial class AppearanceSettingsViewModel : ObservableObject, IDis
                 OnPropertyChanged();
                 OnPropertyChanged(nameof(ColorizationModeIndex));
                 OnPropertyChanged(nameof(IsCustomTintVisible));
-                OnPropertyChanged(nameof(IsCustomTintIntensityVisible));
+                OnPropertyChanged(nameof(IsColorIntensityVisible));
+                OnPropertyChanged(nameof(IsImageTintIntensityVisible));
+                OnPropertyChanged(nameof(EffectiveTintIntensity));
                 OnPropertyChanged(nameof(IsBackgroundControlsVisible));
                 OnPropertyChanged(nameof(IsNoBackgroundVisible));
                 OnPropertyChanged(nameof(IsAccentColorControlsVisible));
+                OnPropertyChanged(nameof(IsResetButtonVisible));
 
                 if (value == ColorizationMode.WindowsAccentColor)
                 {
@@ -179,6 +184,19 @@ public sealed partial class AppearanceSettingsViewModel : ObservableObject, IDis
         {
             _settings.CustomThemeColorIntensity = value;
             OnPropertyChanged();
+            OnPropertyChanged(nameof(EffectiveTintIntensity));
+            Save();
+        }
+    }
+
+    public int BackgroundImageTintIntensity
+    {
+        get => _settings.BackgroundImageTintIntensity;
+        set
+        {
+            _settings.BackgroundImageTintIntensity = value;
+            OnPropertyChanged();
+            OnPropertyChanged(nameof(EffectiveTintIntensity));
             Save();
         }
     }
@@ -279,12 +297,108 @@ public sealed partial class AppearanceSettingsViewModel : ObservableObject, IDis
         };
     }
 
+    public int BackdropOpacity
+    {
+        get => _settings.BackdropOpacity;
+        set
+        {
+            if (_settings.BackdropOpacity != value)
+            {
+                _settings.BackdropOpacity = value;
+                OnPropertyChanged();
+                OnPropertyChanged(nameof(EffectiveBackdropStyle));
+                OnPropertyChanged(nameof(EffectiveImageOpacity));
+                Save();
+            }
+        }
+    }
+
+    public int BackdropStyleIndex
+    {
+        get => (int)_settings.BackdropStyle;
+        set
+        {
+            var newStyle = (BackdropStyle)value;
+            if (_settings.BackdropStyle != newStyle)
+            {
+                _settings.BackdropStyle = newStyle;
+
+                OnPropertyChanged();
+                OnPropertyChanged(nameof(IsBackdropOpacityVisible));
+                OnPropertyChanged(nameof(IsMicaBackdropDescriptionVisible));
+                OnPropertyChanged(nameof(IsBackgroundSettingsEnabled));
+                OnPropertyChanged(nameof(IsBackgroundNotAvailableVisible));
+
+                if (!IsBackgroundSettingsEnabled)
+                {
+                    IsColorizationDetailsExpanded = false;
+                }
+
+                Save();
+            }
+        }
+    }
+
+    /// <summary>
+    /// Gets whether the backdrop opacity slider should be visible.
+    /// </summary>
+    public bool IsBackdropOpacityVisible =>
+        BackdropStyles.Get(_settings.BackdropStyle).SupportsOpacity;
+
+    /// <summary>
+    /// Gets whether the backdrop description (for styles without options) should be visible.
+    /// </summary>
+    public bool IsMicaBackdropDescriptionVisible =>
+        !BackdropStyles.Get(_settings.BackdropStyle).SupportsOpacity;
+
+    /// <summary>
+    /// Gets whether background/colorization settings are available.
+    /// </summary>
+    public bool IsBackgroundSettingsEnabled =>
+        BackdropStyles.Get(_settings.BackdropStyle).SupportsColorization;
+
+    /// <summary>
+    /// Gets whether the "not available" message should be shown (inverse of IsBackgroundSettingsEnabled).
+    /// </summary>
+    public bool IsBackgroundNotAvailableVisible =>
+        !BackdropStyles.Get(_settings.BackdropStyle).SupportsColorization;
+
+    public BackdropStyle? EffectiveBackdropStyle
+    {
+        get
+        {
+            // Return style when transparency/blur is visible (not fully opaque Acrylic)
+            // - Clear/Mica/MicaAlt/AcrylicThin always show their effect
+            // - Acrylic shows effect only when opacity < 100
+            if (_settings.BackdropStyle != BackdropStyle.Acrylic || _settings.BackdropOpacity < 100)
+            {
+                return _settings.BackdropStyle;
+            }
+
+            return null;
+        }
+    }
+
+    public double EffectiveImageOpacity =>
+        EffectiveBackdropStyle is not null
+            ? (BackgroundImageOpacity / 100f) * Math.Sqrt(_settings.BackdropOpacity / 100.0)
+            : (BackgroundImageOpacity / 100f);
+
     [ObservableProperty]
     public partial bool IsColorizationDetailsExpanded { get; set; }
 
     public bool IsCustomTintVisible => _settings.ColorizationMode is ColorizationMode.CustomColor or ColorizationMode.Image;
 
-    public bool IsCustomTintIntensityVisible => _settings.ColorizationMode is ColorizationMode.CustomColor or ColorizationMode.WindowsAccentColor or ColorizationMode.Image;
+    public bool IsColorIntensityVisible => _settings.ColorizationMode is ColorizationMode.CustomColor or ColorizationMode.WindowsAccentColor;
+
+    public bool IsImageTintIntensityVisible => _settings.ColorizationMode is ColorizationMode.Image;
+
+    /// <summary>
+    /// Gets the effective tint intensity for the preview, based on the current colorization mode.
+    /// </summary>
+    public int EffectiveTintIntensity => _settings.ColorizationMode is ColorizationMode.Image
+        ? _settings.BackgroundImageTintIntensity
+        : _settings.CustomThemeColorIntensity;
 
     public bool IsBackgroundControlsVisible => _settings.ColorizationMode is ColorizationMode.Image;
 
@@ -292,16 +406,21 @@ public sealed partial class AppearanceSettingsViewModel : ObservableObject, IDis
 
     public bool IsAccentColorControlsVisible => _settings.ColorizationMode is ColorizationMode.WindowsAccentColor;
 
-    public AcrylicBackdropParameters EffectiveBackdrop { get; private set; } = new(Colors.Black, Colors.Black, 0.5f, 0.5f);
+    public bool IsResetButtonVisible => _settings.ColorizationMode is ColorizationMode.Image;
+
+    public BackdropParameters EffectiveBackdrop { get; private set; } = new(Colors.Black, Colors.Black, 0.5f, 0.5f);
 
     public ElementTheme EffectiveTheme => _elementThemeOverride ?? _themeService.Current.Theme;
 
-    public Color EffectiveThemeColor => ColorizationMode switch
-    {
-        ColorizationMode.WindowsAccentColor => _currentSystemAccentColor,
-        ColorizationMode.CustomColor or ColorizationMode.Image => ThemeColor,
-        _ => Colors.Transparent,
-    };
+    public Color EffectiveThemeColor =>
+        !BackdropStyles.Get(_settings.BackdropStyle).SupportsColorization
+            ? Colors.Transparent
+            : ColorizationMode switch
+            {
+                ColorizationMode.WindowsAccentColor => _currentSystemAccentColor,
+                ColorizationMode.CustomColor or ColorizationMode.Image => ThemeColor,
+                _ => Colors.Transparent,
+            };
 
     // Since the blur amount is absolute, we need to scale it down for the preview (which is smaller than full screen).
     public int EffectiveBackgroundImageBlurAmount => (int)Math.Round(BackgroundImageBlurAmount / 4f);
@@ -309,11 +428,13 @@ public sealed partial class AppearanceSettingsViewModel : ObservableObject, IDis
     public double EffectiveBackgroundImageBrightness => BackgroundImageBrightness / 100.0;
 
     public ImageSource? EffectiveBackgroundImageSource =>
-        ColorizationMode is ColorizationMode.Image
-        && !string.IsNullOrWhiteSpace(BackgroundImagePath)
-        && Uri.TryCreate(BackgroundImagePath, UriKind.RelativeOrAbsolute, out var uri)
-            ? new Microsoft.UI.Xaml.Media.Imaging.BitmapImage(uri)
-            : null;
+        !BackdropStyles.Get(_settings.BackdropStyle).SupportsBackgroundImage
+            ? null
+            : ColorizationMode is ColorizationMode.Image
+              && !string.IsNullOrWhiteSpace(BackgroundImagePath)
+              && Uri.TryCreate(BackgroundImagePath, UriKind.RelativeOrAbsolute, out var uri)
+                ? new Microsoft.UI.Xaml.Media.Imaging.BitmapImage(uri)
+                : null;
 
     public AppearanceSettingsViewModel(IThemeService themeService, SettingsModel settings)
     {
@@ -327,7 +448,7 @@ public sealed partial class AppearanceSettingsViewModel : ObservableObject, IDis
 
         Reapply();
 
-        IsColorizationDetailsExpanded = _settings.ColorizationMode != ColorizationMode.None;
+        IsColorizationDetailsExpanded = _settings.ColorizationMode != ColorizationMode.None && IsBackgroundSettingsEnabled;
     }
 
     private void UiSettingsOnColorValuesChanged(UISettings sender, object args) => _uiDispatcher.TryEnqueue(() => UpdateAccentColor(sender));
@@ -357,6 +478,8 @@ public sealed partial class AppearanceSettingsViewModel : ObservableObject, IDis
         // Theme services recalculates effective color and opacity based on current settings.
         EffectiveBackdrop = _themeService.Current.BackdropParameters;
         OnPropertyChanged(nameof(EffectiveBackdrop));
+        OnPropertyChanged(nameof(EffectiveBackdropStyle));
+        OnPropertyChanged(nameof(EffectiveImageOpacity));
         OnPropertyChanged(nameof(EffectiveBackgroundImageBrightness));
         OnPropertyChanged(nameof(EffectiveBackgroundImageSource));
         OnPropertyChanged(nameof(EffectiveThemeColor));
@@ -379,7 +502,28 @@ public sealed partial class AppearanceSettingsViewModel : ObservableObject, IDis
         BackgroundImageBlurAmount = 0;
         BackgroundImageFit = BackgroundImageFit.UniformToFill;
         BackgroundImageOpacity = 100;
-        ColorIntensity = 0;
+        BackgroundImageTintIntensity = 0;
+    }
+
+    [RelayCommand]
+    private void ResetAppearanceSettings()
+    {
+        // Reset theme
+        Theme = UserTheme.Default;
+
+        // Reset backdrop settings
+        BackdropStyleIndex = (int)BackdropStyle.Acrylic;
+        BackdropOpacity = 100;
+
+        // Reset background image settings
+        BackgroundImagePath = string.Empty;
+        ResetBackgroundImageProperties();
+
+        // Reset colorization
+        ColorizationMode = ColorizationMode.None;
+        ThemeColor = DefaultTintColor;
+        ColorIntensity = 100;
+        BackgroundImageTintIntensity = 0;
     }
 
     public void Dispose()

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/BackdropControllerKind.cs

@@ -0,0 +1,41 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.CmdPal.UI.ViewModels;
+
+/// <summary>
+/// Specifies the type of system backdrop controller to use.
+/// </summary>
+public enum BackdropControllerKind
+{
+    /// <summary>
+    /// Solid color with alpha transparency (TransparentTintBackdrop).
+    /// </summary>
+    Solid,
+
+    /// <summary>
+    /// Desktop Acrylic with default blur (DesktopAcrylicKind.Default).
+    /// </summary>
+    Acrylic,
+
+    /// <summary>
+    /// Desktop Acrylic with thinner blur (DesktopAcrylicKind.Thin).
+    /// </summary>
+    AcrylicThin,
+
+    /// <summary>
+    /// Mica effect (MicaKind.Base).
+    /// </summary>
+    Mica,
+
+    /// <summary>
+    /// Mica alternate/darker variant (MicaKind.BaseAlt).
+    /// </summary>
+    MicaAlt,
+
+    /// <summary>
+    /// Custom backdrop implementation.
+    /// </summary>
+    Custom,
+}

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/BackdropStyle.cs

@@ -0,0 +1,36 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.CmdPal.UI.ViewModels;
+
+/// <summary>
+/// Specifies the visual backdrop style for the window.
+/// </summary>
+public enum BackdropStyle
+{
+    /// <summary>
+    /// Standard desktop acrylic with blur effect.
+    /// </summary>
+    Acrylic,
+
+    /// <summary>
+    /// Solid color with alpha transparency (no blur).
+    /// </summary>
+    Clear,
+
+    /// <summary>
+    /// Mica effect that samples the desktop wallpaper.
+    /// </summary>
+    Mica,
+
+    /// <summary>
+    /// Thinner acrylic variant with more transparency.
+    /// </summary>
+    AcrylicThin,
+
+    /// <summary>
+    /// Mica alternate variant (darker).
+    /// </summary>
+    MicaAlt,
+}

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/BackdropStyleConfig.cs

@@ -0,0 +1,77 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.CmdPal.UI.ViewModels;
+
+/// <summary>
+/// Configuration parameters for a backdrop style.
+/// </summary>
+public sealed record BackdropStyleConfig
+{
+    /// <summary>
+    /// Gets the type of system backdrop controller to use.
+    /// </summary>
+    public required BackdropControllerKind ControllerKind { get; init; }
+
+    /// <summary>
+    /// Gets the base tint opacity before user adjustments.
+    /// </summary>
+    public required float BaseTintOpacity { get; init; }
+
+    /// <summary>
+    /// Gets the base luminosity opacity before user adjustments.
+    /// </summary>
+    public required float BaseLuminosityOpacity { get; init; }
+
+    /// <summary>
+    /// Gets the brush type to use for preview approximation.
+    /// </summary>
+    public required PreviewBrushKind PreviewBrush { get; init; }
+
+    /// <summary>
+    /// Gets the fixed opacity for styles that don't support user adjustment (e.g., Mica).
+    /// When <see cref="SupportsOpacity"/> is false, this value is used as the effective opacity.
+    /// </summary>
+    public float FixedOpacity { get; init; }
+
+    /// <summary>
+    /// Gets whether this backdrop style supports custom colorization (tint colors).
+    /// </summary>
+    public bool SupportsColorization { get; init; } = true;
+
+    /// <summary>
+    /// Gets whether this backdrop style supports custom background images.
+    /// </summary>
+    public bool SupportsBackgroundImage { get; init; } = true;
+
+    /// <summary>
+    /// Gets whether this backdrop style supports opacity adjustment.
+    /// </summary>
+    public bool SupportsOpacity { get; init; } = true;
+
+    /// <summary>
+    /// Computes the effective tint opacity based on this style's configuration.
+    /// </summary>
+    /// <param name="userOpacity">User's backdrop opacity setting (0-1 normalized).</param>
+    /// <param name="baseTintOpacityOverride">Optional override for base tint opacity (used by colorful theme).</param>
+    /// <returns>The effective opacity to apply.</returns>
+    public float ComputeEffectiveOpacity(float userOpacity, float? baseTintOpacityOverride = null)
+    {
+        // For styles that don't support opacity (Mica), use FixedOpacity
+        if (!SupportsOpacity && FixedOpacity > 0)
+        {
+            return FixedOpacity;
+        }
+
+        // For Solid: only user opacity matters (controls alpha of solid color)
+        if (ControllerKind == BackdropControllerKind.Solid)
+        {
+            return userOpacity;
+        }
+
+        // For blur effects: multiply base opacity with user opacity
+        var baseTint = baseTintOpacityOverride ?? BaseTintOpacity;
+        return baseTint * userOpacity;
+    }
+}

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/BackdropStyles.cs

@@ -0,0 +1,65 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.CmdPal.UI.ViewModels;
+
+/// <summary>
+/// Central registry of backdrop style configurations.
+/// </summary>
+public static class BackdropStyles
+{
+    private static readonly Dictionary<BackdropStyle, BackdropStyleConfig> Configs = new()
+    {
+        [BackdropStyle.Acrylic] = new()
+        {
+            ControllerKind = BackdropControllerKind.Acrylic,
+            BaseTintOpacity = 0.5f,
+            BaseLuminosityOpacity = 0.9f,
+            PreviewBrush = PreviewBrushKind.Acrylic,
+        },
+        [BackdropStyle.AcrylicThin] = new()
+        {
+            ControllerKind = BackdropControllerKind.AcrylicThin,
+            BaseTintOpacity = 0.0f,
+            BaseLuminosityOpacity = 0.85f,
+            PreviewBrush = PreviewBrushKind.Acrylic,
+        },
+        [BackdropStyle.Mica] = new()
+        {
+            ControllerKind = BackdropControllerKind.Mica,
+            BaseTintOpacity = 0.0f,
+            BaseLuminosityOpacity = 1.0f,
+            PreviewBrush = PreviewBrushKind.Solid,
+            FixedOpacity = 0.96f,
+            SupportsOpacity = false,
+        },
+        [BackdropStyle.MicaAlt] = new()
+        {
+            ControllerKind = BackdropControllerKind.MicaAlt,
+            BaseTintOpacity = 0.0f,
+            BaseLuminosityOpacity = 1.0f,
+            PreviewBrush = PreviewBrushKind.Solid,
+            FixedOpacity = 0.98f,
+            SupportsOpacity = false,
+        },
+        [BackdropStyle.Clear] = new()
+        {
+            ControllerKind = BackdropControllerKind.Solid,
+            BaseTintOpacity = 1.0f,
+            BaseLuminosityOpacity = 1.0f,
+            PreviewBrush = PreviewBrushKind.Solid,
+        },
+    };
+
+    /// <summary>
+    /// Gets the configuration for the specified backdrop style.
+    /// </summary>
+    public static BackdropStyleConfig Get(BackdropStyle style) =>
+        Configs.TryGetValue(style, out var config) ? config : Configs[BackdropStyle.Acrylic];
+
+    /// <summary>
+    /// Gets all registered backdrop styles.
+    /// </summary>
+    public static IEnumerable<BackdropStyle> All => Configs.Keys;
+}

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/MainWindowViewModel.cs

@@ -22,6 +22,7 @@ public partial class MainWindowViewModel : ObservableObject, IDisposable
     public partial Stretch BackgroundImageStretch { get; private set; } = Stretch.Fill;
 
     [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(EffectiveImageOpacity))]
     public partial double BackgroundImageOpacity { get; private set; }
 
     [ObservableProperty]
@@ -39,6 +40,30 @@ public partial class MainWindowViewModel : ObservableObject, IDisposable
     [ObservableProperty]
     public partial bool ShowBackgroundImage { get; private set; }
 
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(EffectiveBackdropStyle))]
+    [NotifyPropertyChangedFor(nameof(EffectiveImageOpacity))]
+    public partial BackdropStyle BackdropStyle { get; private set; }
+
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(EffectiveBackdropStyle))]
+    [NotifyPropertyChangedFor(nameof(EffectiveImageOpacity))]
+    public partial float BackdropOpacity { get; private set; } = 1.0f;
+
+    // Returns null when no transparency needed (BlurImageControl uses this to decide source type)
+    public BackdropStyle? EffectiveBackdropStyle =>
+        BackdropStyle == BackdropStyle.Clear ||
+        BackdropStyle == BackdropStyle.Mica ||
+        BackdropOpacity < 1.0f
+            ? BackdropStyle
+            : null;
+
+    // When transparency is enabled, use square root curve so image stays visible longer as backdrop fades
+    public double EffectiveImageOpacity =>
+        EffectiveBackdropStyle is not null
+            ? BackgroundImageOpacity * Math.Sqrt(BackdropOpacity)
+            : BackgroundImageOpacity;
+
     public MainWindowViewModel(IThemeService themeService)
     {
         _themeService = themeService;
@@ -58,6 +83,9 @@ public partial class MainWindowViewModel : ObservableObject, IDisposable
             BackgroundImageTintIntensity = _themeService.Current.TintIntensity;
             BackgroundImageBlurAmount = _themeService.Current.BlurAmount;
 
+            BackdropStyle = _themeService.Current.BackdropParameters.Style;
+            BackdropOpacity = _themeService.Current.BackdropOpacity;
+
             ShowBackgroundImage = BackgroundImageSource != null;
         });
     }

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/PreviewBrushKind.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.CmdPal.UI.ViewModels;
+
+/// <summary>
+/// Specifies the brush type to use for backdrop preview approximation.
+/// </summary>
+public enum PreviewBrushKind
+{
+    /// <summary>
+    /// SolidColorBrush with computed alpha.
+    /// </summary>
+    Solid,
+
+    /// <summary>
+    /// AcrylicBrush with blur effect.
+    /// </summary>
+    Acrylic,
+}

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Services/AcrylicBackdropParameters.cs

@@ -1,9 +0,0 @@
-// Copyright (c) Microsoft Corporation
-// The Microsoft Corporation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using Windows.UI;
-
-namespace Microsoft.CmdPal.UI.ViewModels.Services;
-
-public sealed record AcrylicBackdropParameters(Color TintColor, Color FallbackColor, float TintOpacity, float LuminosityOpacity);

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Services/BackdropParameters.cs

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Windows.UI;
+
+namespace Microsoft.CmdPal.UI.ViewModels.Services;
+
+/// <summary>
+/// Parameters for configuring the window backdrop appearance.
+/// </summary>
+/// <param name="TintColor">The tint color applied to the backdrop.</param>
+/// <param name="FallbackColor">The fallback color when backdrop effects are unavailable.</param>
+/// <param name="EffectiveOpacity">
+/// The effective opacity for the backdrop, pre-computed by the theme provider.
+/// For Acrylic style: TintOpacity * BackdropOpacity.
+/// For Clear style: BackdropOpacity (controls the solid color alpha).
+/// </param>
+/// <param name="EffectiveLuminosityOpacity">
+/// The effective luminosity opacity for Acrylic backdrop, pre-computed by the theme provider.
+/// Computed as LuminosityOpacity * BackdropOpacity.
+/// </param>
+/// <param name="Style">The backdrop style (Acrylic or Clear).</param>
+public sealed record BackdropParameters(
+    Color TintColor,
+    Color FallbackColor,
+    float EffectiveOpacity,
+    float EffectiveLuminosityOpacity,
+    BackdropStyle Style = BackdropStyle.Acrylic);

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Services/ThemeSnapshot.cs

@@ -51,12 +51,23 @@ public sealed class ThemeSnapshot
     public required double BackgroundImageOpacity { get; init; }
 
     /// <summary>
-    /// Gets the effective acrylic backdrop parameters based on current settings and theme.
+    /// Gets the effective backdrop parameters based on current settings and theme.
     /// </summary>
-    /// <returns>The resolved <c>AcrylicBackdropParameters</c> to apply.</returns>
-    public required AcrylicBackdropParameters BackdropParameters { get; init; }
+    /// <returns>The resolved <c>BackdropParameters</c> to apply.</returns>
+    public required BackdropParameters BackdropParameters { get; init; }
+
+    /// <summary>
+    /// Gets the raw backdrop opacity setting (0-1 range).
+    /// Used for determining if transparency is enabled and for image opacity calculations.
+    /// </summary>
+    public required float BackdropOpacity { get; init; }
 
     public required int BlurAmount { get; init; }
 
     public required float BackgroundBrightness { get; init; }
+
+    /// <summary>
+    /// Gets whether colorization is active (accent color, custom color, or image mode).
+    /// </summary>
+    public required bool HasColorization { get; init; }
 }

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/SettingsModel.cs

@@ -74,6 +74,8 @@ public partial class SettingsModel : ObservableObject
 
     public int CustomThemeColorIntensity { get; set; } = 100;
 
+    public int BackgroundImageTintIntensity { get; set; }
+
     public int BackgroundImageOpacity { get; set; } = 20;
 
     public int BackgroundImageBlurAmount { get; set; }
@@ -84,6 +86,10 @@ public partial class SettingsModel : ObservableObject
 
     public string? BackgroundImagePath { get; set; }
 
+    public BackdropStyle BackdropStyle { get; set; }
+
+    public int BackdropOpacity { get; set; } = 100;
+
     // END SETTINGS
     ///////////////////////////////////////////////////////////////////////////